Interpretive Summary: Isolated zein has been shown to produce wheat-like dough when mixed at elevated temperatures, or in the presence of plasticizers, and zein-starch mixtures have been successfully used in the production of wheat-free bread. How zein is able to form dough is not fully understood. Thus, the purpose of this research was to investigate various types of protein-protein interactions and their role in zein dough formation. Non-covalent interactions were found to play a critical role in zein’s ability to form dough and zein functionality was very sensitive to salts, such as sodium chloride. This information will be useful in developing both food and industrial products from zein.

Technical Abstract:
Zein has been used in the production of a wide variety of materials during the last century. One of the more intriguing developments in zein utilization has been the discovery that zein can be made to form a visco-elastic dough for bread production. Although significant research has been conducted to determine the functional properties of zein and how to modify these properties, little work has been done to determine how zein forms a visco-elastic dough. To investigate the role of various types of protein-protein interactions in zein’s ability to form a visco-elastic material when mixed with water, several different reagents were added to zein while it was being mixed above its glass transition temperature. The role of hydrophobic interactions was evaluated through the addition of various salts from the Hofmeister series. Urea, ethanol, and beta mercaptoethanol (ß-ME) were also tested to evaluate the effects of protein denaturation and disulfide bonds on zein dough formation. Kosmotropic salts had a negative effect on zein dough formation indicating that increasing hydrophobic interactions prevented dough formation. Surface hydrophobicity was found to decrease significantly (p < 0.05) when zein was exposed to 1M or 2M of the kosmotropic salts. Conversely, chaotropic salts had a slight positive effect on zein dough formation as did urea and ethanol. Interestingly, (ß-ME) had little effect on zein dough formation demonstrating that disulfide bonds played no role in zein dough development and that large disulfide linked polymeric protein complexes were not present as found in wheat and carob germ flour dough.